The reuptake of choline produced by hydrolysis of acetylcholine is necessary for cholinergic function and is thought to be associated specifically with cholinergic terminals and the synthesis of acetylcholine (Ach). Glial cells may modulate synaptic function by participating in the reuptake process for neuronally released transmitters and choline. We propose to more clearly define specificity of choline uptake, and its modulation by glia by the use of several cell lines used as models of normal function. C6 astrocytoma and several clones of neuroblastoma will be used as models of glia and neurons respectively. We will look for the presence or absence of high affinity choline uptake systems in a cholinergic clone of neuroblastoma (SP18) compared to NB41 neuroblastoma, and adrenergic clone. A third clone, NT18, which has neither choline acetylase nor tyrosine hydroxylase, will be used as control. The synthesis of Ach, as related to choline uptake, will be examined by chromatographic identification of products and by direct measurement of Ach and choline in the culture material. Choline uptake will be studied in C6 astrocytoma to more clearly delineate a possible glial role in cholinergic transmission. The hormonal modulation of cholinergic function will be examined by the use of norepinephrine and the cyclic nucleotides (cAMP and cGMP) on choline uptake. The use of NVP (naphthyl vinyl pyrrolidone), and inhibitor of CAT, will dissociate the uptake systems of choline from the synthesis of Ach.